It's hard to recall an episode that was inherently forgettable.
I'd have to say The '37s. Did the aliens who took them ever show up? Did we ever find out why they were taken? Did they just decide to stay on the planet? For me, the answer is "I don't remember, nor do I care." Did Voyager land on the planet for some purpose? Well, they just find the people there, hang out for a bit, and then leave. I don't think anything happened in the long run.
Though, I could just cite any episode where the reset button occurs (Time and Again, Timeless, Year of Hell) because the events of the episode were literally forgettable. You could skip those episodes and miss nothing of the continuity (hahahahahaha).